Industrial applications of use of inkjet printers include wide format printers for digital textile and sign graphics developed in early stages, and are further expanding in recent years into a broader range of industrial and technical fields, for example, digital printing and digital decoration required to deal with different demands ranging from mass production to individual production (production by order).
Among the conventional analog-based printing applications, transition to digital printing is going well with, especially, POD (print-on-demand) mostly targeted for individual printing needs. Yet, analog printing is still a mainstream printing technique in industrial fields and products prioritized in image quality and higher resolution and precision for better marketability.
FIG. 5A is an upper view of a conventional inkjet printing apparatus 101. The inkjet printing apparatus 101 has a head unit 105 from which ink is ejected, and a mounting unit 110 disposed so as to face the head unit 105. The mounting unit 110 supports a lower part of a recording medium 140. The head unit 105 is guided along a guide rail 107 by a main scan driving unit 125 controlled by a controller 120 to perform scans in a main scanning direction (main scans), specifically, Y direction illustrated in FIG. 5A. A sub scan driving unit 155 controlled by the controller 120 drives the head unit 105 to perform scans in a sub scanning direction (sub scans), specifically, X direction illustrated in FIG. 6A. When the head unit 105 is moving fast during the main scans (see FIG. 5B described later), the movement and resulting vibration of the head unit 105 may undermine desired sharpness of a print result.
FIG. 5B is a drawing that illustrates a head gap G in the conventional inkjet printing. FIG. 5B is a front view of the conventional inkjet printing apparatus 101. In the conventional inkjet printing apparatus 101, the head gap G between the head unit 105 and an upper surface of the mounting unit 110 in Z direction on the drawing may be approximately 3 mm. Therefore, any recording mediums having thicknesses W of 1 mm or more may be difficult to use. Therefore, textile printing using thick mediums such as fabric may be often difficult to perform with the inkjet printing apparatus 101.
Japanese Patent No. 5280073 describes a technique to decrease air resistance against ink droplets ejected from the head unit 105 through pressure reduction in a space between the head unit 105 and the mounting unit 110 to allow the ink droplets to land at predesignated positions with higher accuracy even when the head unit and the upper surface of the mounting unit are spaced apart with a larger head gap G.